Jet fuel compositions



m sank 3,089,762 BET FUEL COMPOSETKGNS Harold D. Orloif, Oak Park, andJohn P. Napolitano, Royal Oak, Mich, assignors to Ethyl Corporation, NewYork, N.Y., a corporation of Virginia No Drawing. Filed July 28, 1969,Ser. No. E5396 (Ilaims. (Cl. 44-78) This invention relates to thermallystable jet aircraft fuels, and more particularly to such fuelscontaining methylenebis phenols which are halogen substituted and whichcompounds have outstanding properties as thermal stability additives tojet aircraft fuel.

Fuel temperatures in modern jet aircraft power plants are becoming sohigh that harmful deposits are formed in the precombustion phase of thefuel system. Contribu ting to this has been the practice of using thefuel as a heat sink in connection with cooling the lubricating oil whichha increased fuel temperatures to the point where deposits are so severethat they interfere with normal fuel combustion as well as lubricatingoil temperature control. The jet fuel thermal stability problem is soserious in some fuels that their use can eventually lead to enginefailure of the turbine section due to uneven temperature patterns.

Prior investigators have found that conventional gasoline antioxidantsare incapable of overcoming this problem. For example, it has beenstated that neither 4- methyl-Z,6-di-tert-butylphenol norN,N'-di-sec-butyl-pphenylenediamine, both well-known antioxidants,improves the high temperature stability of jet fuels. Indeed, somegasoline antioxidants have been shown to increase the severity of theproblem. Consequently, other types of additives have been investigated.One approach has been the use of dispersants in an attempt to keep thedeposits suspended in the fuel and thereby prevent them from adhering tocritical engine surfaces. However, this approach has not provedsatisfactory because the deterioration of the fuel does occur under jetengine operating conditions and little, if any, improvements in engineperformance have been attained. Another approach has been tlie hse ofvarious jet fuel treating procedures. These are not always satisfactorybecause they are expensive and complicated, and in many cases, littleimprovement is achieved. Also, many of these additives cause intolerabledifficulties in removal of moisture from jet fuel, and cause seriousfoamy problems.

It is an object of this invention to provide phenolic compounds havingan extremely high degree of efiectiveness as jet fuel thermalstabilizers. Another object of this invention is to alleviate thethermal stability problems in jet fuels. A further object is to providenew jet fuel compositions which are characterized by a high degree ofthermal stability. A still further object is to provide processes ofinhibiting deterioration in jet fuel normally tending to occur atelevated temperatures below the cracking temperature of the fuel duringoperation of the aircraft. A specific object of this invention is theprovision of jet fuel compositions containing the compound 2,2-methylenebis-'(4-chloro-6-tert-butylphenol). Other objects will beapparent from the following description.

3,989,762 Patented May 14, 1963 The objects of this invention areaccomplished by a liquid hydrocarbon jet aircraft fuel, heavier thangasoline, containing from about 0.001 to about 0.2 percent by weight ofa compound having the formula:

Where R is an alkyl group substituted on the alpha carbon atom and whichhas from 4-8 carbon atoms, and X is a halogen selected from the classconsisting of chlorine, bromine and iodine. Thus, the alkyl groups designated by R in the above formula are secondary and tertiary alkyl groupsillustrated by the sec-butyl group, the various secondary hexyl groups,the tertiary butyl, amyl, hexyl, heptyl and octyl groups.

A preferred group of compounds falling within the above class are thosein which the halogen atom designated by X in the above formula ischlorine. These compounds are preferred as they have properties whichrender them outstandingly suited as additives to jet fuel and becausethey are more readily prepared in commercial operations.

Compounds of the above formula in which the alkyl group is a tertiarybutyl group are especially preferred because of their compatibility withvarious organic media, by their ease of preparation and theiroutstanding antioxidant and stabilizing properties. Thus, the mostparticularly preferred compound of this invention is 2,2-

methylenebis-(4-chloro-6-tert-butylphenol) which is both readilyprepared and will be further illustrated below and is an outstandingadditive to jet fuel compositions for increasing the thermal stabilitythereof.

A particularly preferred embodiment of this invention is jet fuelcontaining 2,2'-methylenebis-(4-chloro-6-tertbutylphenol) The thermalstabilizers of this invention exhibit the unique property of greatlyimproving the thermal stability of jet fuels and this effectiveness isindependent of the hydrocarbon types from which the jet fuel has beenprepared. Thus, the present invention affords eXtreme protection againstthermal instability of all present day jet fuels.

The jet fuels of this invention overcome the jet fuel thermalinstability problem by conferring greatly improved thermal stabilitycharacteristics upon the fuels. Thus, a direct benefit accruing from thepractice of this invention is the considerable reduction in the amountof insoluble products formed when the jet fuels of this invention aresubjected to elevated temperatures. Hence, markedly reduced is theamount of insoluble thermal decomposition products which heretoforedeposited in the fuel system. The additives of this invention do notintroduce secondary problems in use, such as forming of the fuel at highaltitudes, emulsification dimculties, interference with low temperatureflow and the like. At the 3 same time, all of these advantages areachieved in a simple manner and at very low cost.

It is known that jet fuels tend to deteriorate when subjected to thecondition of elevated temperatures below the cracking of the fuel, i.e.,temperatures in the range with JP-3. The gravity requirements are from45.0 to 570 API.

JP-S is a high flashpoint type fuel which is an essen-' tiallyfractionated kerosene having a 10 percent evapo- 5 rated minimumtemperature of 400 F. and a maximum f a ut 300 t about 0 Thus, another Pof end point of 550 F. It is heavier than the other fuels, thisinvention is a process of inhibiting such deterioration the gravityrequirements ranging from 3648 API. which comprises subjecting a jetfuel containing from JP-6 is also a distillate fuel having a minimuminitial about (1001 to about Percent y Weight of a boiling point of 250F. and a 90 percent evaporation methylenebis(4-halo-6-alkylphenol) tosaid condition. 10 point maximum of 500 F. The gravity of this fuel mayThus, enhanced thermal stability of a jet fuel is achieved va y f 37,0 t50 APL y blending With the fuel froIn about (1001 to about Otherrequirements of these fuels are as described in Percent y Weight of a yy the military specifications referred to above.

P U- A Preferred range of additive concentration is Recently, however,increased civilian use of jet planes fr m 0. 05 t about (3-05 WeightPercent of Such a has increased the consumption of civilian types of jety y P 1). This conce fuels. These fuels usually conform to ASTMstandards range is preferred as it has been found adequate to very f j ftypes A A 1 d ]3 T A i a id t effectively Stabilize a Vast j y of thefuels gasoline-kerosene blend used for short to medium range The j fuelsWhose thermal Stability is greatly operations, while type A-l is a blendsimilar to type A Proved Pursuant to this invention are Principally Y P'but having a lower freezing point and employed more for carbon fuelswhich are heavier than gasoline, i.e., d1slong range flighw Type B isalso a gasoline-kemsene tilled liquid hydrocarbon fuels having a higherend Peint blend. It is similar to JP-4. While most commercial thangasoline- In general, the j fuels can he eompl'ieed fuels conform tothese ASTM specifications, some equipof distillate fuels and haphthasand blends of the above, ment operations require fuels to have specialproperties including blends with lighter hydrocarbon fractions. not i db h ASTM ifi ti n The end Point of the filial j fuel is above A veryrecent development in fuels for jet aircraft inusually is at least andPreferably greater than volves the use of certain pure hydrocarbon, orblends 480 F. It Will be und however, that the l of hydrocarbons asfuels. Among these are parafiins, fuels which are employed according tothis invention can monocyclic hydrocarbons, polycyclic isolated ring andcontain certain other ingredients such as alcohols or the onde d ringcompounds d t i d t t d h d like, provided the resulting fuel blendmeets the specicarbons, These include bis(methy1cy1ohexy1) ethane fic ip p l fueis- Volatile and y isopropylbicyclohexane,dimethanedecahydronaphthalene, carbon composition requirements of a jetfuel are prin na nd th lik mafily p d y the nature of l engineoperation- Whereas the concentrations of additives of this inven- Thus,it is impossible without catastrophic effects to 5 tion have beendescribed above in terms of weight peremploy an ordinary gasoline as ajet fuel due to the cent of the fuel and this terminology is used in thesubordinarily high volatility of gasoline. sequent examples in thespecification, it is common prac- Until recently, the major use of jetfuels has been in flee to express additive concentrations in pounds permilitary aircraft. The military establishment has im- 1,000 barrels offuel treated. Since the gravity of these posed rigorous standards ofhydrocarbon content and 4.0 fuels varies from about 36 API to 60 API,this exother properties on the fuels according to various classipressionis only approximately precise in terms of weight fio i All of the i fy jfuels are eheol'hpassed percent. For a 36 API gravity fuel, 0.001percent by Wlthul the Scope of thlS invention e y include weightcorresponds roughly to 3.0 pounds per 1,000 bar- JP-3, -h and Therequirements for three rels, whereas for a 60 API gravity fuel 0.001percent of i fuelsi namely IF-4 and are 4r by weight of additive amountsto about 2.6 pounds per bod1ed 1n specification MIL-J-5624-D, datedDecember 0 1000 barrels Thus for a fuel 0 001 Wei ht 24, 1957. JP-6requirements are outlined in specificais from 'about t ab t275 d g 6tion MIL-F-25656 (USAF), dated September 10, 1955. b I d 02 3 Per Ingeneral, JP-3 is referred to as a high vapor pressure arm S an Welghtpercent is eqmvalent to 516450 type fuel which may be a mixturecontaining up to about Pounds: per 1000 barrels In a fuel 0'001 Percent70 percent gasoline and about 30 percent light distillate. by welghtamounts, to about per 1,000 one of the requirements Set forth in themilitary speci barrels and 0.2 we1ght percent 1s equ1valent to 520-560fication is that JP-3 must have a 90 percent evaporation Pounds Per1,000 barrels- For fuel o-ool Pement point minimum at 4 and a ifigravity rangby weight amounts to from 2.753.0 pounds per 1,000 ing f om50 to 0,0 barrels and 0.2 weight percent is equivalent to 550-600 JP-4is a low vapor pressure type fuel which may be pounds per 1,000 barrels,etc. Even though the gravity a mixture of up to about percent gasolineand 35 of the fuels vary, an excellent approximation to the percentdistillate. It is a fuel especially designed for weight percent can beobtained by converting from high altitude performance and also must havea perpounds per 1,000 barrels. cent evaporation minimum temperature at470 F. How- Table I shows the specification of a number of typical ever,in distinction to JP-3 the 20 percent evaporation 60 hydrocarbon jetfuels which are benefited by the practice minimum temperature is 290 F.instead of 240 F. as of this invention.

TABLE I Fuel A Fuel 13 Fuel C Fuel D Fuel E Fuel F Fuel G Fuel H uel(Oom- (JP-4) (.TP5) (JP-4) (JP-4 Re-(Kerosene (Oorn- (JP-5) (JP-5)mercial) ference) Type) mercial) 10 Percent Evaporated, F 380 220 395 2380 376 382 400 90 Percent Evaporated, F- 457 470 480 379 460 480 477403 480 Endpoint, F 490 550 550 480 6 519 496 524 Gravity, API 43. 9 4535 47. 3 4s. 5 43 42. 0 4a. a 41. 2 Existent Gurn,mg./1(l0 n11., max...0. 7 7 7 1. 0 1. 4 1. 7 0. 2 1. 0 0. 6 Potential Gum, mg./10O 1111., max14 14 1.0 9 6 Reid Vapor Pressure, psi 3. 0 0 5 0.5 Aromatics, vol.Percent 14.1 25.0 25.0 12.5 14 6 14.3 13 4 13.5 10.7 Olefins, vol.Percent 5.0 5.0 0.3 1 2 3 0 0. 53 1.0

s eaves Example 1 To 100,000 parts of Fuel A is added with stirring onepart (0.001 percent) of 2,2-methylenebis-(4-chloro-6- tert-butylphenol)dissolved in 20 parts of ethanol. The resulting fuel is found to possessimproved thermal stability characteristics.

Example 2 To 100,000 parts of Fuel B is added 200 parts (0.2 percent of2,2'-methylenebis-(4-bromo 6-isopropylphenol) dissolved in 1,000 partsof methanol. The resulting fuel possesses improved thermal stabilityproperties.

Example 3 With 100,000 parts of Fuel C is blended 5 parts (0.005percent) of 2,2-methylenebis-(4-iodo-6-sec-dodecylphe- 1101). Theresulting fuel blend possesses improved thermal stabilitycharacteristics.

Example 4 To 100,000 parts of Fuel D is added 50 parts (0.05 percent) of2,2-methylenebis-(4-chloro-6-tert-butylphe- I101). The resulting fuelblend is found to possess vastly superior thermal stabilitycharacteristics.

Example 5 With 100,000 parts of Fuel E is blended 80 parts (008 percent)of 2,2-methylenebis-(4-chloro-6-tert-amyiphenol). The resulting fuelblend possesses enhanced thermal stability properties.

Example 6 To 100,000 parts of Fuel F is added 200 parts (0.2 percent) of2,'2-methylenebis-(4-bromo-6-sec-octylphenol) dissolved in 1,500 partsof isopropanol. After mixing, the resulting fuel blend is found topossess enhanced thermal stability properties.

Example 7 Example 8 To 100,000 parts of Fuel H is added 150 parts (0.15percent) of 2,Z'-methy1enebis-[4-iodo-6-(1,1,3,3-te amethylbutyl)phenol]dissolved in 1,500 parts of mixed Xylenes. The resulting jet fuelpossesses superior thermal stability properties.

Example 9 With 100,000 parts of Fuel B is blended 60 parts (0.06percent) of 2,2'-methylenebis-(4-chloro-6-sec-butylphe- 1101). This fuelafter mixing possesses improved thermal stability characteristics.

Example 10 170 parts of 2,2-methylenebis-(4-chloro-6-tert-butylphenol)is blended with 100,000 parts of Fuel 1. The resulting jet fuelcontaining 0.17 percent of the phenol possesses improved thermalstability characteristics.

Example 11 With 100,000 parts of Fuel C is blended 70 parts (0.07percent) of 2,2-me-thylenebis-(4-chloro-5-tert-butylphen01). Theresulting jet fuel blend possesses superior thermal stabilitycharacteristics.

Example 12 To 10,000 parts of Fuel H is added with agitation 160 parts(0.16 percent) of 2,2-methylenebis-(4-bromo-6- sec-octylphenol). Theresulting fuel is found to have greatly improved thermal stabilitycharacteristics.

Example 13 To show the great improvements in thermal stability resultingfrom the practice of this invention, tests were conducted in anapparatus known as the Coordinating Fuel Research (CFR) Jet Fuel Coker,commonly called the Erdco Rig. The test procedure and equipment aredescribed in Petroleum Processing, December 1955, pages 1909-1911, andin Coordinating Research Council Manual No. 3. In this equipment a jetfuel under 150 pounds pressure is forced through a pre-heater tubehaving a centrally located heating element to raise the temperature ofthe fuel to a predetermined point. The heated fuel is then forcedthrough a hot filter of sintered steel into a second tube. When thermaldecomposition of the fuel occurs at the elevated temperature, the filterbecomes plugged and a pressure drop occurs across the filter. Thispressure drop is measured by a manometer placed across the filter. Thefollowing tests were conducted until a pressure drop across the fuelfilter of 25" of mercury caused by decomposition of the fuel and filterplugging occurred, or if a pressure drop of 25" of mercury did not occuracross the filter within 300 minutes, the tests were discontinued. Inall tests the fuel flow rate was maintained at 6 pounds per hour.

let fuels of this invention were prepared by blending2,2'-methylenebis-(4-chloro6-tert-butylphenol), the most particularlypreferred compound of this invention, with samples of three differentcommercially available JP-S fuels which meet all of the requirements ofthe above mentioned military specification except for the thermalstability properties. In these tests on JP-S, a sample of each of thefuels without a thermal stability additive of this invention was alsotested. The test conditions were adjusted so that the pre-heatertemperature was 400 F. and the filter temperature was 500 F. The resultsof these tests are shown in Table 11.

TABLE Il.lP-5 FUELS WITH AND WITHOUT 2,2'- THIOBIS-6-TERT-BUTYL-4-CHLOROPHENOL) 2.2-Methylenebls (G-tert- Pressure Time ofFuel butyl--chlorm Across Fi1- Test, min.

phenol) Cone, tcr, inches lbs/1,000 bbl.

The data in Table II indicate that outstanding improvements in thermalstability were achieved in both of the above fuels by the additionrespectively of 100 and 50 pounds per 1,000 barrels of the fuels tested.However, in addition to the great improvement in the alleviation offilter plugging, other benefits accrue from the practice of thisinvention. Fuel J containing no additive, deteriorated to such an extentduring the 91 minute test that the pro-heater tube was coated withblack, dark brown and tan decomposition products to the extent of 20percent of the surfaces thereof. However, with the addition of poundsper 1,000 barrels of 2,2-methylenebis-(4-chloro-6-tert-butylphenol), thedeposits were reduced to a very light tan color indicating the amazingimprovement in the condition of deposit on the preheater tubes.Similarly, in Fuel K during the 39 minutes of the test on the fuel whichcontained no additive, a total of 70 percent of the pro-heater surfaceswere coated "with deposits ranging in character from dark brown to lighttan. However, with the addition of 50 pounds per 1,000 barrels of thepreferred additive of this invention, the total deposit area was reducedto 10 percent after a 300 minute period and the deposit ranged incharacter from light tan to brown. In both of these instances, greatimprovement in the fuel was achieved by the use of the especiallypreferred additive of this invention, 2,2'-methylenebis-( l-chloro 6tert-butylphe- 1101).

Example 14 To further demonstrate the effects of the additives of thisinvention on the thermal stability properties of jet fuels, a test wasrun in a commercially available ZIP-4 fuel. In this test the pro-heatertemperature was adjusted to 300 F. and the filter was maintained at 400F. Other test conditions were as described above. The fuel with noadditive developed 25" of mercury pressure drop across the filter in 109minutes and during this time 40 percent of the pro-heater surfaces werecovered with deposits ranging from brown to tan. However, when 25 poundsper 1,000 barrels of 2,2'-methylenebis-(4-chloro- 6-tert-butylphenol)was added to this fuel, a total pressure drop of only 0.1" of mercuryaccrued over a 300 minute period. Furthermore, the pro-heater surfaceswere completely clean under these conditions. This test furtherdemonstrates the outstanding ability of the compounds of this inventionto alleviate jet fuel thermal stability problems even at lowconcentrations of additive. With other compounds of this inventionsimilar results are obtained.

As noted above the amount of the additive of this invention used in jetaircraft fuels can range from about 0.001 to about 0.2 percent byweight. Ordinary concentrations varying from 0.005 to about 0.05 weightpercent of additive are found to be satisfactory for most present dayfuels. Variations from these concentration ranges are permissible andsometimes desirable. For example, in jet fuels initially possessing afair degree of thermal stability, very small amounts of additive aresulficient to improve the characteristics in order to meet the militaryspecifications, and in some cases, provide improved storage stabilityproperties. On the other hand, where the jet fuel initially has a verypoor thermal stability, larger amounts-up to 0.2 percent by weight ormore-can be effectively employed.

Typical jet fuel thermal stability additives of this invention include2,2-methylenebis-(4-chloro-6isopropylphenol), 2,2-methylenebis-(4-bromo=6-sec-butylphenol) 2,2'-methylenebis-(4 chloro-6tert-butylphenol), 2,2- methylenebis-(4-iodo-6-sec-amylphenol),2,2'-rnethylenebis-(4-chloro-6-tert-hexylphenol), 2,2 methylenebis-(lbromo-6-tert-butylphenol), 2,2-methylenebis-(4-iodo-6-sec-heptylphenol), and the like. As noted above the chloro compounds arepreferred and the preferred alkyl group is the tertiary butyl group.

In preparing the improved fuels of this invention, the use of solventsfor the 2,2-methylenebis-(4-ha1o-6-alkyl phenol) compounds is sometimesadvantageous. While the solubility of these compounds in jet fuel issufficiently high to provide the desired concentrations blendingprocedures may be simplified by pre-dissolving the additives in asuitable solvent. The resulting concentrates can then be convenientlyand readily blended with the jet fuels while all the components are inthe liquid phase. Suitable solvents for this purpose include botharomatic and aliphatic hydrocarbons, alcohols and ketones. In general,ketones and alcohols containing up to 6 carbon atoms and liquid aromatichydrocarbons containing 6 to 18 carbon atoms are suitable solvents. Theyinclude, for example, benzene, toluene, xylenol, acetone, methyl ethylketone, methanol, diethyl ketone, ethanol, isopropanol, methyl isobutylcarbonyl and the like.

In addition to the 2,2-methylenebis-(4-halo-6-alkylphenol) thermalstabilizer of this invention, jet fuels may have added to them suchother materials as anti-rust additives, dispersants, dyes, and ingeneral other additives which do not adversely effect the thermalstability of the fuel.

The 2,2'-methylcnebis-(4-halo 6 alkylphenol) compounds used in thisinvention are prepared for example by a process which comprises reactinga 4-halo-6-alkylphenol having the formula:

where X is a halogen such as chlorine, bromine and iodine and R is analkyl group which is branched on the alpha carbon atom which containsfrom 48 carbon atoms, formaldehyde in the presence of an alkali metalhydroxide and a non-aqueous solvent. This reaction is illustrated by thefollowing example for the preferred compound of this invention.

Example 15 In a reaction vessel equipped with reflux condenser, heatingmeans, means for agitating reactants and means for charging liquidreactants was placed 3142 parts of isopropanol and 66 parts of potassiumhydroxide. The mixture was agitated until the potassium hydroxide wascompletely dissolved at which point 1846 parts of4-chloro-6-tert-butylphenol was added and the mixture was heated to 45C. While maintaining the temperature 420 parts of a 36.3 percentformalin solution was added incrementally. The reaction temperature wasthereafter maintained with agitation for 6 hours, cooled to roomtemperature and acidified with about 200 parts of dilute hydrochloricacid. The acidified mixture was added to about 5500 parts of petroleumether, the isopropanol was extracted with Water and the water phasediscarded. The organic phase was then distilled through a helix packedcolumn and 665 parts of 2,2'-methylenebis-(4- chloro-6-tert-butylphenol)were recovered at 209-2l3 C. at 0.3 ml. pressure. A portion of thismaterial was recrystallized from petroleum ether to yield white crystalsof pure 2,2'-methylenebis(4-chloro-6-tert-butylphenol) having a meltingpoint of 114-1145 C. Upon analysis these crystals were found to contain64 percent carbon, 6.6 percent hydrogen and 19.6 percent chlorine. Thecalculated content for the compound is 66.1 percent carbon, 6.8 percenthydrogen and 18.6 percent chlorine. An infrared spectrum of the compoundshowed bands of a partially hindered hydroxyl of a bisphenol compound.The ring substitution as determined from the infrared spectrum showedthe compound to contain a 1,2,4,6-substituted benzene ring.

We claim:

1. A thermally stabilized distilled hydrocarbon jet fuel having an endpoint, higher than gasoline, of at least 480 F. and an API gravity,higher than hydrocarbon mineral lubricating oil, of from 35-50",containing from about 0.01 to about 5 percent by weight of a compoundhaving the formula:

OH OH i R- (|J-- R H l I X X where R is an alpha-branched alkyl groupwhich has 20 10 from 4-8 carbon atoms, and X is a halogen selected fromthe class consisting of chlorine, bromine and iodine.

5. A process for cooling the lubricating oil in a jet engine comprisingusing as a coolant for heat transfer With the lubricating oil athermally stabilized jet fuel consisting essentially of a distilledhydrocarbon fuel having an end point of at least about 480 F. andcontaining from about 0.01 to about 0.1 percent by weight of 2.2-methylenebis-(4-chloro-6-tert-butylphenol) References Cited in the fileof this patent UNITED STATES PATENTS 2,542,972 Thompson Feb. 27, 19512,734,088 Knowles et a1. Feb. 7, 1956 2,829,175 Bowman et a1. Apr. 1,1958 2,841,627 Beaver et a1. July 1, 1958 2,932,942 Ecke et a1. Apr. 19,1960 2,959,915 Dille et a1 Nov. 15, 1960 3,012,049 Bill Dec. 5, 1961

1. A THERMALLY STABILIZED DISTILLED HYDROCARBON JET FUEL HAVING AN ENDPOINT, HIGHER THAN GASOLINE, OF AT LEAST 480* F. AND AN API GRAVITY,HIGHER THAN HYDROCARBON MINERAL LUBRICATING OIL, OF FROM 35-50* ,CONTAINING FROM ABOUT 0.01 TO ABOUT 5 PERCENT BY WEIGHT OF A COMPOUNDHAVING THE FORMULA: